This invention relates to gas turbine combustor technology and more especially to a gas turbine fuel nozzle construction with enhanced internal flow path design.
In a typical “can-annular” type gas turbine combustor arrangement, several combustors are arranged in an annular array about the turbine rotor axis and supply combustion gases to the first stage of the turbine. A compressor pressurizes inlet air which is then turned in direction (or reverse flowed) to the combustor where it is used to cool the hot gas path components and to provide air to the combustion process. Each combustor assembly comprises a generally cylindrical combustor (incorporating a combustor chamber), a fuel injection system, and a transition piece or duct that guides the flow of the hot combustion gas from the combustor to the inlet of the turbine section. Gas turbines of this type typically may include 6, 10, 14 or 18 combustors arranged about the turbine rotor axis.
One specific dry low NOx emission combustion system includes a fuel injection system for each combustor which is comprised of multiple fuel nozzles supported on an end cover that closes the upstream end of the combustor. Each fuel nozzle includes a swirler and a radially oriented peg assembly downstream of the swirler. The swirler and peg assembly may be a one-piece casting or a multi-piece casting or fabricated assembly, and there are typically 8-10 pegs extending radially away from the fuel nozzle body. Each hollow peg has a teardrop outer shape and an internal round bore supplying fuel to multiple holes or orifices by which the fuel is injected into the combustion chamber. The radially outer ends of the pegs are closed by plugs which cover one or more of the orifices, requiring additional drilling through the plugs to re-open the orifices. In addition, the plugs cause an unwanted internal “step” in the flow path. At the same time, and for certain other low NOx combustion systems, higher fuel flows must be accommodated while maintaining a predetermined fuel supply pressure and the same exterior shape and dimensions. Thus, the internal passages must be enhanced to accommodate the higher flows while maintaining the outer geometry substantially unchanged.
In one exemplary but non-limiting embodiment, there is provided a nozzle for gas turbine comprising a tubular nozzle body; and a plurality of hollow fuel injection pegs extending radially from the tubular nozzle body at a location between forward and aft ends of the tubular nozzle body; wherein each of the plurality of hollow fuel injection pegs has an external tear-drop cross-sectional shape, and a fuel passage in each of the hollow injection pegs has a substantially matching internal tear-drop cross-sectional shape.
In another exemplary but non-limiting embodiment, there is provided a nozzle for a gas turbine comprising a tubular nozzle body; and a plurality of hollow fuel injection pegs extending radially from the tubular nozzle body at a location between forward and aft ends of the tubular nozzle body; a plurality of hollow fuel injection pegs extending substantially perpendicularly radially from the tubular nozzle body at a location between the forward and aft ends; and wherein the tubular nozzle body has a base flange attached to a forward end thereof, the base flange formed with an annular array of elongated arcuate fuel inlet slots for supplying fuel to a passage in the tubular nozzle body which connects to the plurality of fuel injection pegs.
In yet another exemplary but non-limiting embodiment, there is provided the nozzle for a gas turbine comprising a tubular body; and a plurality of hollow fuel injection pegs extending radially from the tubular nozzle body at a location between forward aft ends of the tubular nozzle body; wherein each of the plurality of hollow fuel injection pegs has a radially outer end wall, wherein a fuel passage in each of the hollow injection pegs has a substantially smooth surface extending continuously between said tubular nozzle body and the radially outer end wall.
The invention will now be described in greater detail in connection with the drawings identified below.
With reference to
More specifically, each combustor 14 includes a substantially cylindrical combustor casing 18 which is secured to the turbine casing 20 by means of, for example, bolts 22. The forward end of the combustor casing is closed by an end cover assembly 24 which may include conventional supply tubes, manifolds and associated valves (indicated generally at 26), etc. for feeding gas, liquid fuel and air (and water if desired) to the combustion chamber. The end cover assembly 24 receives a plurality (for example, five) of diffusion/premix fuel nozzle assemblies 28 (only one shown for purposes of convenience and clarity) arranged in a circular array about a longitudinal axis of the combustor.
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In addition, the radial bore in the prior externally tear-drop shaped fuel injector pegs 42 were round, and located in the wider or leading edge of the tear-drop-shaped peg. In the reconfigured peg, the internal radial passage 68 is matched to the external tear-drop shape, thereby increasing the internal volume of the peg and, in effect, creating a plenum for more accurately optimal feeding of the plural injector holes 70 in the peg.
At the same time, enlarging the internal volume of the passage 68 during the blind casting or other fabrication process employed to make the swirler (36, 40, 42), also makes it possible to create an integral tip or end wall 72, thereby eliminating a commonly found step or shoulder 74 in plug (integral or added) 76 utilized to close the remote end of the fuel injection peg 78 (see
The above-described flow enhancements enable the nozzle to handle higher flows with minimum modifications; minimizes unwanted pressure losses; and permits optimization of the fuel injection profile.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.